Typical fluorescent lamps for interior office lighting, for instance, employ a fairly simple inductive ballast for regulating current flow through the lamps. The current flow is regulated to be at some constant, resulting in constant lamp power. The cathodes of such lamps are typically filament-heated, and thus are double-ended. The cathodes are designed to be continually heated as long as the lamps are conducting.
Fairly sophisticated ballast circuits have been designed to enable a user to change the current level, and hence, power level of the lamps. Such ballast circuits, however, in addition to being costly of themselves, require installation by skilled electricians, for instance. This adds to the cost of such circuits.